Stator assembly of hairpin winding motor

ABSTRACT

A stator assembly of a hairpin winding motor capable of improving the performance of the winding motor and the insulation performance of a hairpin coil, including a stator core through which a plurality of slots pass in a circumferential direction; and a plurality of hairpin coils respectively fastened to and interconnected with the slots to form a coil winding. The hairpin coil includes a head portion bent in a U shape and exposed to the outside of the stator core, and a pair of leg portions configured to extend in parallel from both ends of the head portion to be inserted into a specific slot and the slot spaced apart from the specific slot by one pole pitch and of which end portions are exposed to the outside of the stator core.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.16/726,903 filed on Dec. 25, 2019, which claims priority from and thebenefit of Korean Patent Application No. 10-2019-0001253, filed on Jan.4, 2019, which are hereby incorporated by reference for all purposes asif it set forth herein.

BACKGROUND Field

Exemplary embodiments relate to a stator assembly of a hairpin windingmotor, and more particularly, to a stator assembly of a hairpin windingmotor capable of improving the performance of the winding motor and theinsulation performance of a hairpin coil.

Discussion of the Background

Research and development, and commercialization of eco-friendlyautomobile-related parts have actively proceeded in the automobileindustry according to international demands for greenhouse gas reductionregulation and improvement of fuel efficiency of automobiles.

A technology for exerting a driving force using an electric motor is indevelopment as a kind of an eco-friendly automobile-related part, andespecially for this, a motor-producing technology emphasizing improvedmotor operating efficiency is also required.

Carmakers and manufacturers of eco-friendly parts apply hairpin coils todriving motors as a part of technology development to reduce the weightand volume of each of the eco-friendly parts.

Due to development of a technology for reducing the weight and volume ofeach of the eco-friendly parts, the weight of a vehicle or aneco-friendly vehicle can be reduced, and an inner space can be secured.

According to a method of manufacturing a drive motor to which a hairpincoil is applied according to the related art, unlike a general motor inwhich a coil is wound, the hairpin coil is molded or formed in aU-shaped shape so that a coil or ring having a generally angularcross-section can be inserted into a slot of the stator core in advance,thereby making the hairpin coil.

Accordingly, since a conventional hairpin coil has a lower productionyield than a circular coil, and a film may be damaged or reduced inthickness in the process of forming a coil with high load while twistingand bending a coil having an angular cross-sectional area to wind thehairpin coil, insulation performance can be degraded.

Meanwhile, the stator core is formed of a magnetic material, andincludes a yoke forming a magnetic path and a tooth protruding radiallyinward from the yoke.

A plurality of teeth are formed along a circumferential direction.

A slot is formed between the teeth, and substantially, the hair pin coilis inserted into the slot to form a stator coil.

When the hairpin coil according to the related art is designed to insertan angular coil having the same thickness and width into a stator slot,since the teeth become thick in a direction toward the yoke forming themagnetic path in the stator core, and the teeth become thin in adirection opposite the direction toward the yoke, design constraints ofa stator assembly are incurred.

Accordingly, when a motor is operated under a load condition, thedirection toward the yoke in which the teeth are thick has a lowmagnetic flux density, but the direction opposite the direction towardthe yoke in which the teeth are thin easily saturates and thus,performance is degraded.

Further, since the film is thinned or damaged during the process offorming the coil with high load while twisting and bending a coil havinga rectangular cross-sectional area to wind the hairpin, insulationperformance is degraded.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Exemplary embodiments of the present invention provide a stator assemblyof a hairpin winding motor capable of improving the performance of thewinding motor and the insulation performance of a hairpin coil.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

An exemplary embodiment of the present invention provides a statorassembly of a hairpin winding motor including: a stator core throughwhich a plurality of slots are formed to pass therethrough in acircumferential direction; and a plurality of hairpin coils respectivelyfastened to, and interconnected with, the slots to form a coil winding.Each of the hairpin coils includes a head portion bent in a U shape andexposed to the outside of the stator core, and a pair of leg portionsconfigured to extend in parallel from both ends of the head portion tobe inserted into a specific slot and the slot spaced apart from thespecific slot by one pole pitch and of which end portions are exposed tothe outside of the stator core.

The stator core may include a yoke formed of a magnetic material andforming a magnetic path, and a plurality of teeth inwardly protrudingradially inward from an inner circumferential surface of the yoke alonga circumferential direction to form the slot, the slot may be formed tohave a trapezoidal shape, in which the outside is broad and the insideis narrow, and a cross-sectional shape of each of the teeth may beformed to have a rectangular shape.

The two leg portions of the hairpin coil disposed adjacent to each otherin a circumferential direction may be welded to each other.

A cross-section of the head portion may be formed in a circular shape,and a cross-section of each of the pair of leg portions may be formed tohave a trapezoidal shape, in which the outside is broad and the insideis narrow.

A cross-sectional area of the head portion may be roughly 2 to 20%greater than cross-sectional areas of the leg portions.

The leg portions may be formed through a rolling process.

The hairpin coils may be formed of a first coil inserted into the slottoward the yoke, a second coil inserted into the slot opposite the yokewith respect to the first coil, a third coil inserted into the slotopposite the yoke with respect to the second coil, and a fourth coilinserted into the slot opposite the yoke with respect to the third coil.

Cross-sectional areas of the leg portion of the first coil, the legportion of the second coil, the leg portion of the third coil, and theleg portion of the fourth coil may be the same.

Another exemplary embodiment of the present invention provides a statorassembly of a hairpin winding motor including: a stator core in which aplurality of slots are formed to pass therethrough in a circumferentialdirection; and a plurality of hairpin coils respectively fastened to andinterconnected with the slots to form a coil winding. Each of thehairpin coils includes a head portion exposed to the outside of thestator core at one end thereof, and a leg portion configured to extendfrom the other end of the head portion to be inserted into the slot andof which an end portion is exposed to the outside of the stator core.

The two head portions repeatedly inserted into a specific slot and theslot spaced apart from the specific slot by one pole pitch along acircumferential direction, and disposed adjacent to each other in acircumferential direction may be welded to each other, and the two legportions disposed adjacent to each other in a circumferential directionmay be welded to each other, in the plurality of the hairpin coils.

A cross-section of the head portion may be formed in a circular shape,and a cross-section of the leg portion may be formed to have atrapezoidal shape, in which the outside is broad and the inside isnarrow.

A cross-sectional area of the head portion may be roughly 2 to 20%greater than a cross-sectional area of the leg portion.

Each of the cross-section of the head portion and the cross-section ofthe leg portion may be formed to have a trapezoidal shape, in which theoutside is broad and the inside is narrow.

Cross-sectional areas of the head portion and the leg portions may bethe same.

The head portion and the leg portion may be formed through a rollingprocess.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a perspective view illustrating a hairpin coil of a statorassembly of a hairpin winding motor according to a first exemplaryembodiment of the present invention.

FIG. 2 is a schematic view for comparing cross-sectional areas of a headportion and leg portions of the hairpin coil according to the firstexemplary embodiment of the present invention.

FIG. 3 is a plan view illustrating a flat surface of the stator assemblyof the hairpin winding motor according to the first exemplary embodimentof the present invention.

FIGS. 4A and 4B are views respectively illustrating saturation of thestator assembly of the hairpin winding motor according to the relatedart and the first exemplary embodiment of the present invention.

FIG. 5 is a perspective view illustrating a hairpin coil of a statorassembly of a hairpin winding motor according to a second exemplaryembodiment of the present invention.

FIG. 6 is a perspective view illustrating a hairpin coil of a statorassembly of a hairpin winding motor according to another exemplaryembodiment of the present invention.

FIG. 7 is a plan view illustrating a flat surface of the stator assemblyof the hairpin winding motor according to the second exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which embodiments of the invention are shown.This invention may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure isthorough, and will fully convey the scope of the invention to thoseskilled in the art. Like reference numerals in the drawings denote likeelements.

The embodiments are only provided to completely disclose the presentdisclosure and completely convey the scope of the present disclosure tothose skilled in the art, and the present disclosure is defined by thedisclosed claims. Meanwhile, terms used in the description are providednot to limit the present disclosure but to describe the embodiments. Inthe embodiment, the singular form is intended to also include the pluralform unless the context clearly indicates otherwise. The terms“comprise” and/or “comprising” as used herein do not preclude thepresence or addition of at least one other component, step, operation,and/or element other than the stated components, steps, operationsand/or elements.

Hereinafter, a first exemplary embodiment of the present disclosure willbe described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view illustrating a hairpin coil of a statorassembly of a hairpin winding motor according to the first exemplaryembodiment of the present invention. FIG. 2 is a schematic view forcomparing cross-sectional areas of a head portion and leg portions ofthe hairpin coil according to the first exemplary embodiment of thepresent invention. FIG. 3 is a plan view illustrating a flat surface ofthe stator assembly of the hairpin winding motor according to the firstexemplary embodiment of the present invention. FIGS. 4A and 4B arecomparative views respectively illustrating saturation of the statorassembly of the hairpin winding motor according to the related art andthe first exemplary embodiment of the present invention.

Referring to FIGS. 1 to 4B, the stator assembly of the hairpin windingmotor according to the first exemplary embodiment includes a stator core100 and a hairpin coil 200.

A plurality of slots 130 pass through the stator core 100 in an axialdirection along a circumferential direction.

The stator core 100 includes a yoke 110 and teeth 120.

The yoke 110 is formed of a magnetic material, forms a magnetic path,and forms a body of the stator core 100.

Further, the yoke 110 is formed in a closed-loop shape to support theteeth 120.

A plurality of teeth 120 protrude radially inward from an innercircumferential surface of the yoke 110 along a circumferentialdirection and thus, the slots 130 are each formed between the teeth 120.

The plurality of teeth 120 may be continuously disposed in thecircumferential direction of the yoke 110 or radially to form a circularring shape as a whole.

Meanwhile, since the teeth 120 are formed on the inner circumferentialsurface of the yoke 110, the slots 130 formed by the teeth 120 areopened in an inward direction and closed in an outward direction by theyoke 110.

Further, the slot 130 is formed to have a trapezoidal shape, in whichthe outside is broad and the inside is narrow, and a cross-sectionalshape of each of the teeth 120 is formed in a rectangular shape.

That is, since the trapezoidally-shaped slots 130 are formed along thecircumferential direction of the yoke 110, which is formed to have acircular shape, cross-sectional shapes of the teeth 120 are each formedto be rectangular, and thus, cross-sectional thicknesses of the teeth120 are formed to be the same.

The hairpin coil 200 is formed in plural to be respectively fastened toand interconnected with the slots 130 to form a coil winding, and a rawcoil coated with a coating and having a straight length of apredetermined diameter, is processed through a coil processing machine,thereby having connection portions connected to each other.

Further, a cross-sectional shape of the hairpin coil 200 is formed to becircular.

Accordingly, the hairpin coil 200 of FIG. 4B may have an improved yieldand reduced production costs in comparison with a conventional hairpincoil 200 of FIG. 4A in which a cross-sectional shape is formed to berectangular.

Further, in the hairpin coil 200 of which the cross-sectional shape isformed to be circular, the likelihood of damage to a film incurredduring twisting and bending work may be reduced.

The hairpin coil 200 includes a head portion 210 and leg portions 220.

The head portion 210 is bent in a U shape and exposed to the outside ofthe stator core 100 and serves as a connection portion configured toconnect a pair of leg portions 220.

Further, the pair of leg portions 220 extend from both ends of the headportion 210 in parallel and are inserted into the slots 130, and endportions of the leg portions 220 are exposed to the outside of thestator core 100.

Specifically, in one hairpin coil 200, the leg portion 220 in one enddirection among the pair of leg portions 220 which extend from both endsof the head portion 210 is inserted into a specific slot 130 of thestator core 100, and the leg portion 220 in the other end direction isinserted into the slot 130 at a position spaced from the specific slot130 by one pole pitch.

Like the above, the plurality of hairpin coils 200 are respectivelyinserted into the slots 130 along the circumferential direction.

Further, the two leg portions 220 of the hairpin coil 200 disposedadjacent to each other in the circumferential direction are welded toeach other.

Meanwhile, a cross-section of the head portion 210 is formed in acircular shape, and each cross-section of the pair of leg portions 220is formed to have a trapezoidal shape.

More specifically, the leg portion 220 is formed to have a trapezoidalshape in which the outside is broad and the inside is narrow.

Accordingly, a space between an outer side surface of the leg portion220 of the hairpin coil 200 and an inner side surface of the slot 130 isremoved.

Accordingly, as shown in FIG. 4B, since saturation of the stator core100 is maintained at a level of 1.84T to 1.86T by increasing a spacefactor between the leg portions 220 and the slot 130, magnetic fluxdensity is nearly uniform, and thus, the output performance of a drivingmotor may be improved.

Further, preferably, in the hairpin coil 200, only regions of the legportions 220 may be manufactured through a rolling process using acircular coil.

Accordingly, in the hairpin coil 200, the cross-sectional shape of thehead portion 210 may be maintained to be circular, and thecross-sectional shape of each of the leg portions 220 may be easilymanufactured to be trapezoidal.

Although the present exemplary embodiment describes that the legportions 220 are manufactured through a rolling method, the leg portions220 may be manufactured through various methods in addition to therolling method as long as the cross-sections of the leg portions 220 mayeach be manufactured to have a trapezoidal shape, which is the same asthe cross-section of the slot 130.

Meanwhile, as shown in FIG. 2, the cross-sectional area of the headportion 210 is greater than the cross-sectional area of each of the legportions 220.

More specifically, the cross-sectional area of the head portion 210 isformed to be roughly 2 to 20% greater than the cross-sectional area ofeach of the leg portions 220.

The hairpin coils 200 are formed of a first coil 200_1 to a fourth coil200_4 according to insertion positions of the leg portion 220 when thepair of leg portions 220 are inserted into the specific slot 130 and theslot 130 spaced apart from the specific slot 130 by one pole pitch.

More specifically, as shown in FIG. 3, the hairpin coils 200 are formedof the first coil 200_1 of which the pair of leg portions 220 areinserted into the slot 130 in a direction toward the yoke 110, thesecond coil second coil 200_2 of which the pair of leg portions 220 areinserted into the slot 130 opposite the yoke 110 with respect to thefirst coil 200_1, the third coil 200_3 of which the pair of leg portions220 are inserted into the slot 130 opposite the yoke 110 with respect tothe second coil 200_2, and the fourth coil 200_4 of which the pair ofleg portions 220 are inserted into the slot 130 opposite the yoke 110with respect to the third coil 200_3.

Further, cross-sectional areas of the first coil 200_1 to the fourthcoil 200_4 are formed to be the same.

However, the cross-sectional areas of the first coil 200_1 to the fourthcoil 200_4 are the same but shapes of the first coil 200_1 to the fourthcoil 200_4 become different according to the insertion positions intothe slots 130.

Accordingly, since the hairpin coils 200, of which the first coil 200_1to the fourth coil 200_4 have the same cross-sectional area, are usedinstead of the hairpin coils 200 of which the first coil 200_1 to thefourth coil 200_4 have different cross-sectional areas, to manufacturethe hairpin coils 200 according to the present exemplary embodimentformed of the first coil 200_1 to the fourth coil 200_4, manufacturingcosts may be reduced.

Further, an overall cross-sectional shape of each of the leg portions220 of the first coil 200_1 to the fourth coil 200_4 inserted into thespecific slots 130 is formed to be trapezoidal, corresponding to across-sectional shape of the specific slot 130, of which the outside isbroad and the inside is narrow.

Accordingly, since the overall cross-sectional shape of each of the legportions 220 of the first coil 200_1 to the fourth coil 200_4 and thecross-sectional shape of the specific slot 130 are the same, the outputperformance of the driving motor due to resistance reduction may beimproved by increasing the space factor between the leg portions 220 andthe slot 130.

Hereinafter, a second exemplary embodiment of the present invention willbe described in detail with reference to the accompanying drawings.

FIG. 5 is a perspective view illustrating a hairpin coil of a statorassembly of a hairpin winding motor according to the second exemplaryembodiment of the present invention. FIG. 6 is a perspective viewillustrating a hairpin coil of a stator assembly of a hairpin windingmotor according to another exemplary embodiment of the presentinvention. FIG. 7 is a plan view illustrating a flat surface of thestator assembly of the hairpin winding motor according to the secondexemplary embodiment of the present invention.

Referring to FIGS. 5 to 7, the stator assembly of the hairpin windingmotor according to the second exemplary embodiment includes a statorcore 100′ and a hairpin coil 200′.

A plurality of slots 130′ pass through the stator core 100′ in an axialdirection along a circumferential direction.

The stator core 100′ includes a yoke 110′ and teeth 120′.

The yoke 110′ is formed of a magnetic material, forms a magnetic path,and forms a body of the stator core 100′.

Further, the yoke 110′ is formed in a closed-loop shape to support theteeth 120′.

A plurality of teeth 120′ protrude radially inward from an innercircumferential surface of the yoke 110′ along a circumferentialdirection and thus, the slots 130′ are each formed between the teeth120′.

The plurality of teeth 120′ may be continuously disposed in thecircumferential direction of the yoke 110′ or radially to form acircular ring shape as a whole.

Meanwhile, since the teeth 120′ are formed on the inner circumferentialsurface of the yoke 110′, the slots 130′ formed by the teeth 120′ areopened in an inward direction and closed in an outward direction by theyoke 110′.

Further, the slot 130′ is formed in a trapezoidal shape of which theoutside is broad and the inside is narrow, and a cross-sectional shapeof each of the teeth 120′ is formed in a rectangular shape.

That is, since the trapezoidally-shaped slots 130′ are formed along thecircumferential direction of the yoke 110′ which is formed to have acircular shape, cross-sectional shapes of the teeth 120′ are each formedto have a rectangular shape, and thus, cross-sectional thicknesses ofthe teeth 120 become the same.

Accordingly, since saturation of the stator core 100′ is maintained at alevel of about 1.84T to 1.86T, magnetic flux density is uniform, andthus, the output performance of a driving motor may be improved.

A plurality of the hairpin coils 200′ are formed to be respectivelyfastened to and interconnected with the slots 130′ to form a coilwinding, and a raw coil coated with a coating and having a straightlength of a predetermined diameter is processed through a coilprocessing machine.

Further, a cross-sectional shape of the hairpin coil 200′ is formed tobe circular.

Accordingly, the hairpin coil 200′ may have an improved yield andreduced production costs in comparison with a conventional hairpin coil200′ of which a cross-sectional shape is formed to be rectangular.

Further, in the hairpin coil 200′ of which the cross-sectional shape isformed to is have the circular shape, damage to a film during bendingmay be reduced.

The hairpin coil 200′ includes a head portion 210′ and a leg portion220′.

The head portion 210′ is formed at one end of the hairpin coil 200′, andis exposed to the outside of the stator core 100′, the leg portion 220′is formed at the other end of the hairpin coil 200′, and is exposed tothe outside of the stator core 100′ after extending from the other endof the head portion 210′ and being inserted into the slot 130′.

Meanwhile, the hairpin coils 200′ formed in plural are repeatedlyinserted into a specific slot 130′ and the slot 130′ spaced one polepitch from the specific slot 130′ along a circumferential direction.

Further, two head portions 210′ disposed adjacent to each other in acircumferential direction are welded to each other, and two leg portions220′ disposed adjacent to each other in a circumferential direction arewelded to each other.

Meanwhile, a cross-section of the head portion 210′ is formed to have acircular shape, and a cross-section of the leg portion 220′ is formed tohave a trapezoidal shape.

More specifically, the leg portion 220′ is formed to have a trapezoidalshape, of which the outside is broad and the inside is narrow.

Accordingly, since a space between an outer side surface of the legportion 220′ of the hairpin coil 200′ and an inner side surface of theslot 130′ is removed, the output performance of a driving motor due toresistance reduction may be improved by increasing a space factorbetween the leg portion 220′ and the slot 130′.

Further, preferably, in the hairpin coil 200′, only a region of the legportion 220′ may be manufactured through a rolling process using acircular coil.

Accordingly, in the hairpin coil 200′, the cross-sectional shape of thehead portion 210′ may be circular, and the leg portion 220′ may beeasily manufactured to have a trapezoidal cross-sectional shape.

Although the present exemplary embodiment describes that the leg portion220′ is manufactured through a rolling method, the leg portion 220′ maybe manufactured through various methods in addition to the rollingmethod as long as the cross-section of the leg portion 220′ may bemanufactured to have a trapezoidal shape the same as the cross-sectionof the slot 130′.

Meanwhile, the cross-sectional area of the head portion 210′ is greaterthan the cross-sectional area of the leg portion 220′.

More specifically, the cross-sectional area of the head portion 210′ isformed to be roughly 2 to 20% greater than the cross-sectional area ofthe leg portion 220′.

Accordingly, when the hairpin coil 200′ is inserted into the slot 130′,since the head portion 210′ is engaged with an upper surface of thetooth 120′, a length in which the hairpin coil 200′ is inserted into theslot 130′ may be a uniform length, and thus, a height of an end coil maybe uniformly managed.

Meanwhile, although a case in which the circular-shaped head portion210′ is formed at one end of the hairpin coil 200′ and thetrapezoidal-shaped leg portion 220′ is formed at the other end of thehairpin coil 200′ is described in the second exemplary embodiment, inanother exemplary embodiment, as shown in FIG. 6, the cross-sectionalshape of the head portion 210′ may be formed to be trapezoidal, similarto the leg portion 220′.

In this case, the cross-sectional areas of the head portion 210′ and theleg portion 220′, each formed to have the trapezoidal shape, are formedto be the same.

Further, the head portion 210′ and the leg portion 220′ each formed tohave the trapezoidal shape may be simultaneously manufactured through arolling process.

The hairpin coils 200′ are formed of a first coil 200_1′ to a fourthcoil 200_4′ according to insertion positions of the leg portion 220′when the leg portion 220′ is inserted into the specific slot 130.

More specifically, as shown in FIG. 7, the hairpin coils 200′ are formedof the first coil 200_1′ of which the leg portion 220′ is inserted intothe slot 130′ in a direction toward the yoke 110′, the second coilsecond coil 200_2′ of which the leg portion 220′ is inserted into theslot 130′ opposite the yoke 110′ with respect to the first coil 200_1′,the third coil 200_3′ of which the leg portion 220′ is inserted into theslot 130′ opposite the yoke 110′ with respect to the second coil 200_2′,and the fourth coil 200_4′ of which the leg portion 220′ is insertedinto the slot 130′ opposite the yoke 110′ with respect to the third coil200_3′.

Further, cross-sectional areas of the first coil 200_1′ to the fourthcoil 200_4′ are formed to be the same.

However, although the cross-sectional areas of the first coil 200_1′ tothe fourth coil 200_4′ are the same, the shapes of the first coil 200_1′to the fourth coil 200_4′ become different according to the insertionpositions into the slots 130′.

Accordingly, since the hairpin coils 200′ of which the first coil 200_1′to the fourth coil 200_4′ have the same cross-sectional area are usedinstead of the hairpin coils 200′ of which the first coil 200_1′ to thefourth coil 200_4′ have the different cross-sectional areas tomanufacture the hairpin coils 200′ according to the present inventionformed of the first coil 200_1′ to the fourth coil 200_4′, manufacturingcosts may be reduced.

Further, an overall cross-sectional shape of the leg portion 220′ of thefirst coil 200_1′ to the fourth coil 200_4′ inserted into the specificslots 130′ is formed to have a is trapezoidal shape, corresponding to across-sectional shape of the specific slot 130′, of which the outside isbroad and the inside is narrow.

Accordingly, since the overall cross-sectional shape of the leg portion220 of the first coil 200_1′ to the fourth coil 200_4′ and thecross-sectional shape of the specific slot 130′ are the same, the outputperformance of the driving motor due to resistance reduction may beimproved by increasing the space factor between the leg portion 220′ andthe slot 130′.

As described above, in the stator assembly of the hairpin winding motoraccording to the present invention, since the cross-sectional shape ofthe hairpin coil 200 or 200′ is formed to be circular, a yield may beimproved, production costs may be reduced, and damage to the film duringthe twisting or bending work may be reduced.

Further, since the leg portion 220 or 220′ is formed to have thetrapezoidal shape of which the outside is broad and the inside isnarrow, the magnetic flux density of the stator core 100 or 100′ isuniform, and thus, the output performance of the driving motor may be simproved by increasing the space factor between the leg portion 220 or220′ and the slot 130 or 130′.

In addition, in the hairpin coil 200 or 200′, since only the region ofthe leg portion 220 or 220′ is manufactured through the rolling processusing the circular coil, the cross-sectional shape of the head portion210 or 210′ may be maintained to be circular, and the cross-sectionalshape of the leg portion 220 or 220′ may be easily manufactured to havethe trapezoidal shape.

In addition, since the overall cross-sectional shape of the leg portion220 or 220′ of the first coil 200_1 or 200_1′ to the fourth coil 200_4or 200_4′ and the cross-sectional shape of the specific slot 130 or 130′are the same, the output performance of the driving motor due to isresistance reduction may be improved by increasing the space factorbetween the leg portion 220 or 220′ and the slot 130 or 130′.

In addition, since the cross-sectional area of the head portion 210′ isformed to be roughly 2 to 20% greater than the cross-sectional area ofthe leg portion 220′, when the hairpin coil 200′ is inserted into theslot 130′, the head portion 210′ is engaged with an upper surface of thetooth 120′and thus, the length in which the hairpin coil 200′ isinserted into the slot 130′ may be a uniform length, thereby uniformlymanaging the height of the end coil.

In a stator assembly of a hairpin winding motor according to the presentinvention, since a cross-sectional shape of a hairpin coil is formed tobe circular, a yield can be improved, production costs can be reduced,and damage to a film during twisting or bending can be reduced.

Further, since a leg portion is formed to have a trapezoidal shape, ofwhich the outside is broad and the inside is narrow, magnetic fluxdensity of a stator core is uniform by increasing a space factor betweenthe leg portion and a slot, and accordingly, the output performance of adriving motor can be improved.

Further, since only a region of the leg portion of the hairpin coil ismanufactured through a rolling process using a circular coil, across-sectional shape of a head portion can be maintained to becircular, and the leg portion can be easily manufactured to have across-sectional shape in a trapezoid shape.

In addition, since an overall cross-sectional area of each of the legportions of a first coil to a fourth coil and a cross-sectional area ofthe slot are the same, there is an effect of improving the output of thedriving motor due to resistance reduction by increasing the space factorbetween the leg portion and the slot.

In addition, since the cross-sectional area of the head portion isformed to be roughly 2 to 20% greater than the cross-sectional area ofthe leg portion, when the hairpin coil is inserted into the slot, thehead portion is engaged with an upper surface of the tooth and thus, alength in which the hairpin coil is inserted into the slot can be auniform length, and accordingly, a height of an end coil can beuniformly managed.

The present invention is not limited to the above-described embodimentsand may be variously modified within the scope of the technical spiritof the present invention.

What is claimed is:
 1. A stator assembly of a hairpin winding motor,comprising: a stator core including a plurality of slots passingtherethrough in a circumferential direction; and a plurality of hairpincoils respectively fastened to and interconnected with the slots to forma coil winding, wherein: each of the hairpin coils includes a headportion bent in a U-shape and exposed to the outside of the stator core;and a pair of leg portions configured to extend in parallel from bothends of the head portion to be inserted into a specific slot and theslot spaced apart from the specific slot by one pole pitch, and of whichend portions are exposed to the outside of the stator core; and across-sectional area of the head portion is greater than cross-sectionalareas of the leg portions.
 2. The stator assembly of claim 1, wherein across-sectional area of the head portion is about 2 to 20% greater thancross-sectional areas of the leg portions.
 3. The stator assembly ofclaim 1, wherein: the head portion is formed to have a circularcross-sectional shape; and each of the pair of leg portions is formed tohave a trapezoidal cross-sectional shape, of which the outside is broadand the inside is narrow.
 4. The stator assembly of the claim 3, whereinthe pair of leg portions has the trapezoidal cross-section in contactwith the circular cross-section of the head portion.
 5. The statorassembly of the claim 1, wherein: the hairpin coil is manufactured usingan electric wire having a circular cross section; and the head portionis formed by bending the electric wire and the leg portions is formed byrolling an end of the electric wire.